What are the classifications of circuit breakers? Introduction to the working principle of circuit breaker

Speaking of circuit breakers, many people will not be moved by strangers. As the name implies, it is a circuit protection device to avoid personal injury caused by improper operation, but if you really want to tell the details of it, and answer it accurately. What is the circuit breaker, or let a lot of people feel confused. When choosing electrical components such as circuit breakers for home decoration, due to the safety of electricity, when friends choose circuit breakers and other products, they also need to master some common sense in this regard to ensure the quality of the products purchased. The following small series introduces in detail the principle and selection method of the circuit breaker.

1. Introduction to the circuit breaker

A circuit breaker is actually a switch, but the state of the switch is not artificially controlled, but is controlled by a circuit. Under normal working conditions, the switch is in a closed state, and when a serious overload or short circuit or under voltage failure occurs in the circuit, the switch is automatically disconnected to protect the device and the line. Its function is equivalent to the combination of fuse switch and overheat thermal relay, and has been widely used.

2. Classification of circuit breakers

The circuit breaker is generally composed of a contact system, an arc extinguishing system, an operating mechanism, a trip unit, a casing, etc., and can be divided into two types: a universal circuit breaker and a plastic case circuit breaker. At present, the universal circuit breaker in China mainly produces DWI5. , DWI6, DWI7 (ME), DW45 and other series, plastic shell circuit breakers mainly produce DZ20, CMI, TM30 and other series. Circuit breakers can be divided into high-voltage circuit breakers and low-voltage circuit breakers according to their range of use, but the high and low voltage boundary lines are relatively fuzzy. Generally, voltages exceeding 3kV are called high-voltage circuit breakers, and in our daily life, low-voltage circuit breakers are widely used. .

3. Working principle of low voltage circuit breaker

Low-voltage circuit breakers, also known as automatic air switches, can be used to control motors that are infrequently activated and are an important protection device in low-voltage distribution networks. The main contacts of the low voltage circuit breaker are either manually operated or electrically closed. After the main contact is closed, the free trip mechanism locks the main contact in the closed position. The coil of the overcurrent release and the thermal element of the thermal trip are connected in series with the main circuit, while the coil of the undervoltage release is connected in parallel with the power supply.

When the circuit is short-circuited or severely overloaded, the armature of the overcurrent release pulls in, causing the free trip mechanism to act and the main contact to open the main circuit. When the circuit is overloaded, the heat element of the thermal tripper generates heat to deform the bimetal, and when it is deformed to a certain extent, the free trip mechanism is pushed to open and the switch is opened. When the circuit is under voltage, the armature release of the undervoltage release will also cause the free trip mechanism to act and open the switch.

4. Working principle of high voltage circuit breaker

Compared with the low-voltage circuit breaker, the arc-breaking arc is the core work to be completed because the arc to be disconnected can still burn without being extinguished after being elongated. The arc extinguishing is mainly to weaken the free arc while cooling the arc, strengthen the recombination and diffusion movement of the charged particles, and blow off the charged particles in the arc gap, so that the dielectric strength of the medium can be quickly restored. Protective effects.

5. The working principle of the basic circuit breaker

The simplest circuit protection device is a fuse, that is, a very thin wire is attached to the circuit after being attached to the protective cover. This fuse can be blown after the temperature reaches a certain level, causing an open circuit. The circuit breaker is also a circuit protection device, but it can be used repeatedly, unlike a fuse, it can only be used once. The working principle of the basic circuit breaker is as follows: the current can magnetize the electromagnet, and the magnetic force generated by the electromagnet increases with the increase of the current. When the current increases to a dangerous level, the magnetic force generated by the electromagnet also increases accordingly, and the linkage is linked with the switch. The metal rod connected to the device disconnects the switch, interrupting the current and protecting the circuit. The bimetal strip also uses a similar principle to achieve protection of the circuit. At high currents, the metal strip is deformed, and when it is deformed to a certain extent, the linkage device is activated to open the switch. Some circuit breakers also rely on filling explosives to achieve control of the switch. When the current exceeds a certain point, the explosive material is ignited and the switch is opened.

6. Working principle of enhanced circuit breaker

Enhanced circuit breakers eliminate simple electrical equipment and use semiconductor equipment to monitor current levels. For example, the Ground Fault Circuit Interrupter (GFCI) not only protects the wiring of the house from damage, but also protects people from clicks. GFCI constantly monitors the current on the neutral and live lines in the circuit. When the two are the same, they are in normal working condition, and if the currents are different (if someone accidentally touches the live line, the current on the live line increases sharply, and If the current on the neutral line does not change, the circuit will be cut off immediately to prevent an accident. Since GFCI can take action without waiting for the current to rise to dangerous levels, its response speed is much faster than conventional circuit breakers.

7. Circuit breaker purchase

In household power supply, the circuit breaker is usually used as a main power protection switch or a branch line protection switch. If the line or household appliance is short-circuited or overloaded, the circuit breaker can automatically trip and cut off the power supply, thus effectively protecting these devices from damage and reducing the accident to a minimum. It is important to choose the rated capacity current of the circuit breaker in the home. When selecting or checking the total value of the total load current, the average household should pay attention to the value of each branch current and the total load current is the sum of the branch currents. Knowing the branch current and total current, you can choose the specifications of the branch breaker and the total breaker. To ensure safety and reliability, the rated working current of the electrical components should generally be greater than 2 times the required load current.

The above is a brief introduction to the working principle and selection method of the circuit breaker. I believe that everyone has their own one-hand scale on how to choose the circuit breaker. Household circuit breakers are related to the safety of home life, so when choosing a household circuit breaker, you must consult a professional to buy which type of circuit breaker, and also pay attention to the brand of the circuit breaker, the large brand of electrical components It is a powerful guarantee for electricity safety.